It's one of the most anticipated moments of pregnancy. Here's when ultrasound can reveal your baby's sex — and how much to trust the answer.
The Timeline
- Before 14 weeks: External anatomy is not reliably distinguishable. (Some sonographers use the "nub theory" angle at 12–13 weeks, but accuracy is variable and most clinics won't call it.)
- 16 weeks onward: Determination becomes possible in good conditions
- 18–22 weeks (the anomaly scan): The classic window — anatomy is clear, and accuracy in good views is generally quoted at 95% or higher
What Affects Accuracy
- Baby's position — legs crossed or breech positioning can hide the view entirely
- Umbilical cord sitting between the legs (a classic mimic)
- Amniotic fluid levels and maternal body habitus
- Gestational age — earlier means less certain
An experienced sonographer will tell you honestly if the view isn't good enough to call, rather than guess.
Important to Know
- Sex determination is an optional extra during a diagnostic scan, not its purpose — the anomaly scan's job is checking your baby's health
- You can ask the sonographer not to reveal it if you want a surprise — tell them at the start
- Blood-based NIPT testing can indicate sex from about 10 weeks with very high accuracy, if earlier answers matter to you
This article is for general information only and is not a substitute for professional medical advice.
Ready to Book Your Ultrasound Scan?
Mascot Healthcare Clinic, Akoka (Yaba), Lagos offers ultrasound scans by appointment only, Monday–Saturday, 9am–5pm. Book online and choose a time that works for you.